Competing Ordered Phases in URu2Si2: Hydrostatic Pressure and Re-substitution

A persistent kink in the pressure dependence of the \hidden order" (HO) transition temperature of URu2-xRexSi2 is observed at a critical pressure Pc=15 kbar for 0 < x < 0.08. In URu2Si2, the kink at Pc is accompanied by the destruction of superconductivity; a change in the magnitude of a spin excitation gap, determined from electrical resistivity measurements; and a complete gapping of a portion of the Fermi surface (FS), inferred from a change in scattering and the competition between the HO state and superconductivity for FS fraction

The Li Overabundance of J37: Diffusion or Accretion?

In September 2002 the discovery of a super Li-rich F-dwarf (J37) in NGC 6633, an iron poor analogue of the better studied Hyades and Praecepe open clusters, was announced. This unique star was thought to be the smoking gun for the action of diffusion, models of which predict a narrow "Li-peak" at approximately the correct temperature. However, with more detailed studies into J37s abundance pattern this star provides firm evidence for the accretion of planetesimals or other material from the circumstellar environment of new born stars. Thanks to the specific predictions made about the behaviour of Be abundances, (the most striking of which being no Be in super-Li-rich dwarfs subject to diffusion) the opposing diffusion/accretion predictions can be tested. Initial modelling of the Be line indicates that J37 is as Be rich as it is Li rich; log N(Be) = 2.25 +/- 0.25, and so is broadly consistent with an accretion-fuelled enhancement. However, that both Li and Be are enhanced by much more than the iron-peak elements (as determined in previous studies) suggests that diffusion also plays a role in increasing the abundances of Li and Be specifically. Furthermore, a new data set from the UVES/UT2 combination has allowed the elemental abundance of Iron to be measured, and the set of preliminary stellar parameters determined; Teff ~ 7340 K, log g ~ 4.1, microturbulence ~ 4.3 km/s, [Fe/H] ~ 0.50. This again provides distinct evidence for the effects of accretion in J37 and requires a new synthesis of the Be doublet.Comment: 5 pages, 2 figures. Poster presented at IAU Symposium 224 "The A Star Puzzle", 7-13 July 2004, Poprad, Slovaki

Beryllium Enhancement as Evidence for Accretion in a Lithium-Rich F Dwarf

The early F dwarf star ``J37'' in the open cluster NGC6633 shows an unusual pattern of photospheric abundances, including an order of magnitude enhancement of lithium and iron-peak elements, but an under-abundance of carbon. As a consequence of its thin convection zone these anomalies have been attributed to either radiative diffusion or the accretion of hydrogen-depleted material. By comparing high resolution VLT/UVES spectra of J37 (and other F stars in NGC 6633) with syntheses of the Be ii doublet region at 3131 Ang, we establish that J37 also has a Be abundance (A(Be)=3.0+/-0.5) that is at least ten times the cosmic value. This contradicts radiative diffusion models that produce a Li over-abundance, as they also predict photospheric Be depletion. Instead, since Be is a highly refractory element, it supports the notion that J37 is the first clear example of a star that has accreted volatile-depleted material with a composition similar to chondritic meteorites, although some diffusion may be necessary to explain the low C and O abundances.Comment: Accepted for publication in MNRAS letters, 5 page

Final report of the Pearling Industry Review Committee to the Hon. Julian Grill, Western Australian Minister for Fisheries and Hon. John Kerin, M.P. Federal Minister for Primary Industries and Energy.

In October 1987 an Interim Report was issued to enable the present licence holders, the Licensed Pearl Producers\u27 Association and other who had expressed an interest to the Committee, to consider the interim recommendations and , if necessary, make written comment to the Committee. The Committee considered the comments it received. It now presents its Final Report to the Western Australian Minister for Fisheries, the Hon. Julian Grill and the Federal Minister for Primary Industries and Energy, the Hon. John Kerin. The Committee is recommending that the industry be quota controlled with entry by transfer only. The present licence holders plus new applicants yet to be determined are recommended as the companies to comprise those engaged in the industry. The Committee is also recommending that the north west coast be divided into two sectors - one south of Port Hedland, the other north of Port Hedland to the Northern Territory border. the Northern Sector would be zoned to (a) ensure that the very important Eighty Mile Beach area is protected against overfishing and (b) to allow a number of present licence holders to increase their overall catch by fishing in the areas north of Broome

Lithium in Blanco1: Implications for Stellar Mixing

We obtain lithium abundances for G and K stars in Blanco 1, an open cluster with an age similar to, or slightly younger than, the Pleiades. We critically examine previous spectroscopic abundance analyses of Blanco 1 and conclude that while there were flaws in earlier work, it is likely that Blanco 1 is close in overall metallicity to the older Hyades cluster and more metal-rich than the Pleiades. However, we find Blanco 1 has Li abundances and rotation rates similar to the Pleiades, contradicting predictions from standard stellar evolution models, in which convective pre-main sequence (PMS) Li depletion should increase rapidly with metallicity. If the high metallicity of Blanco 1 is subsequently confirmed, our observations imply (1) that a currently unknown mechanism severely inhibits PMS Li depletion, (2) that additional non-standard mixing modes, such as those driven by rotation and angular momentum loss, are then responsible for main sequence Li depletion between the ages of Blanco 1 and the Hyades, and (3) that in clusters younger than the Hyades, metallicity plays only a minor role in determining the amount of Li depletion among G and K stars. These conclusions suggest that Li abundance remains a useful age indicator among young (less than 700 Myr) stars even when metallicities are unknown. If non-standard mixing is effective in Population I stars, the primordial Li abundance could be significantly larger than present day Population II Li abundances, due to prior Li depletion.Comment: 18 pages, 3 figs. To appear in ApJ Vol. 511 (Jan 20 1999

Temporal dynamics of aquatic communities and implications for pond conservation

Conservation through the protection of particular habitats is predicated on the assumption that the conservation value of those habitats is stable. We test this assumption for ponds by investigating temporal variation in macroinvertebrate and macrophyte communities over a 10-year period in northwest England. We surveyed 51 ponds in northern England in 1995/6 and again in 2006, identifying all macrophytes (167 species) and all macroinvertebrates (221 species, excluding Diptera) to species. The alpha-diversity, beta-diversity and conservation value of these ponds were compared between surveys. We find that invertebrate species richness increased from an average of 29. 5 species to 39. 8 species between surveys. Invertebrate gamma-diversity also increased between the two surveys from 181 species to 201 species. However, this increase in diversity was accompanied by a decrease in beta-diversity. Plant alpha-, beta and gamma-diversity remained approximately constant between the two periods. However, increased proportions of grass species and a complete loss of charophytes suggests that the communities are undergoing succession. Conservation value was not correlated between sampling periods in either plants or invertebrates. This was confirmed by comparing ponds that had been disturbed with those that had no history of disturbance to demonstrate that levels of correlation between surveys were approximately equal in each group of ponds. This study has three important conservation implications: (i) a pond with high diversity or high conservation value may not remain that way and so it is unwise to base pond conservation measures upon protecting currently-speciose habitats; (ii) maximising pond gamma-diversity requires a combination of late and early succession ponds, especially for invertebrates; and (iii) invertebrate and plant communities in ponds may require different management strategies if succession occurs at varying rates in the two groups

High nutrient transport and cycling potential revealed in the microbial metagenome of australian sea lion (neophoca cinerea) faeces

Metagenomic analysis was used to examine the taxonomic diversity and metabolic potential of an Australian sea lion (Neophoca cinerea) gut microbiome. Bacteria comprised 98% of classifiable sequences and of these matches to Firmicutes (80%) were dominant, with Proteobacteria and Actinobacteria representing 8% and 2% of matches respectively. The relative proportion of Firmicutes (80%) to Bacteriodetes (2%) is similar to that in previous studies of obese humans and obese mice, suggesting the gut microbiome may confer a predisposition towards the excess body fat that is needed for thermoregulation within the cold oceanic habitats foraged by Australian sea lions. Core metabolic functions, including carbohydrate utilisation (14%), protein metabolism (9%) and DNA metabolism (7%) dominated the metagenome, but in comparison to human and fish gut microbiomes there was a significantly higher proportion of genes involved in phosphorus metabolism (2.4%) and iron scavenging mechanisms (1%). When sea lions defecate at sea, the relatively high nutrient metabolism potential of bacteria in their faeces may accelerate the dissolution of nutrients from faecal particles, enhancing their persistence in the euphotic zone where they are available to stimulate marine production. © 2012 Lavery et al